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From: Andrii Nakryiko <andriin@fb.com>
To: <andrii.nakryiko@gmail.com>, <bpf@vger.kernel.org>,
	<netdev@vger.kernel.org>, <ast@fb.com>, <daniel@iogearbox.net>,
	<kernel-team@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Subject: [PATCH bpf-next 5/8] libbpf: split initialization and loading of BTF
Date: Mon, 10 Jun 2019 21:47:44 -0700
Message-ID: <20190611044747.44839-6-andriin@fb.com> (raw)
In-Reply-To: <20190611044747.44839-1-andriin@fb.com>

Libbpf does sanitization of BTF before loading it into kernel, if kernel
doesn't support some of newer BTF features. This removes some of the
important information from BTF (e.g., DATASEC and VAR description),
which will be used for map construction. This patch splits BTF
processing into initialization step, in which BTF is initialized from
ELF and all the original data is still preserved; and
sanitization/loading step, which ensures that BTF is safe to load into
kernel. This allows to use full BTF information to construct maps, while
still loading valid BTF into older kernels.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5e7ea7dac958..79a8143240d7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1118,7 +1118,7 @@ static void bpf_object__sanitize_btf_ext(struct bpf_object *obj)
 	}
 }
 
-static int bpf_object__load_btf(struct bpf_object *obj,
+static int bpf_object__init_btf(struct bpf_object *obj,
 				Elf_Data *btf_data,
 				Elf_Data *btf_ext_data)
 {
@@ -1137,13 +1137,6 @@ static int bpf_object__load_btf(struct bpf_object *obj,
 				   BTF_ELF_SEC, err);
 			goto out;
 		}
-		bpf_object__sanitize_btf(obj);
-		err = btf__load(obj->btf);
-		if (err) {
-			pr_warning("Error loading %s into kernel: %d.\n",
-				   BTF_ELF_SEC, err);
-			goto out;
-		}
 	}
 	if (btf_ext_data) {
 		if (!obj->btf) {
@@ -1159,7 +1152,6 @@ static int bpf_object__load_btf(struct bpf_object *obj,
 			obj->btf_ext = NULL;
 			goto out;
 		}
-		bpf_object__sanitize_btf_ext(obj);
 	}
 out:
 	if (err || IS_ERR(obj->btf)) {
@@ -1170,6 +1162,26 @@ static int bpf_object__load_btf(struct bpf_object *obj,
 	return 0;
 }
 
+static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
+{
+	int err = 0;
+
+	if (!obj->btf)
+		return 0;
+
+	bpf_object__sanitize_btf(obj);
+	bpf_object__sanitize_btf_ext(obj);
+
+	err = btf__load(obj->btf);
+	if (err) {
+		pr_warning("Error loading %s into kernel: %d.\n",
+			   BTF_ELF_SEC, err);
+		btf__free(obj->btf);
+		obj->btf = NULL;
+	}
+	return 0;
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 {
 	Elf *elf = obj->efile.elf;
@@ -1301,9 +1313,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 		pr_warning("Corrupted ELF file: index of strtab invalid\n");
 		return -LIBBPF_ERRNO__FORMAT;
 	}
-	err = bpf_object__load_btf(obj, btf_data, btf_ext_data);
+	err = bpf_object__init_btf(obj, btf_data, btf_ext_data);
 	if (!err)
 		err = bpf_object__init_maps(obj, flags);
+	if (!err)
+		err = bpf_object__sanitize_and_load_btf(obj);
 	if (!err)
 		err = bpf_object__init_prog_names(obj);
 	return err;
-- 
2.17.1


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-11  4:47 [PATCH bpf-next 0/8] BTF-defined BPF map definitions Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 1/8] libbpf: add common min/max macro to libbpf_internal.h Andrii Nakryiko
2019-06-15 20:26   ` Song Liu
2019-06-11  4:47 ` [PATCH bpf-next 2/8] libbpf: extract BTF loading and simplify ELF parsing logic Andrii Nakryiko
2019-06-15 20:25   ` Song Liu
2019-06-15 20:28     ` Song Liu
2019-06-17 17:46       ` Andrii Nakryiko
2019-06-17 17:24     ` Andrii Nakryiko
2019-06-17 18:07       ` Song Liu
2019-06-17 18:35         ` Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 3/8] libbpf: refactor map initialization Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 4/8] libbpf: identify maps by section index in addition to offset Andrii Nakryiko
2019-06-11  4:47 ` Andrii Nakryiko [this message]
2019-06-15 21:21   ` [PATCH bpf-next 5/8] libbpf: split initialization and loading of BTF Song Liu
2019-06-11  4:47 ` [PATCH bpf-next 6/8] libbpf: allow specifying map definitions using BTF Andrii Nakryiko
2019-06-15 22:00   ` Song Liu
2019-06-17 18:33     ` Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 7/8] selftests/bpf: add test for BTF-defined maps Andrii Nakryiko
2019-06-15 22:05   ` Song Liu
2019-06-11  4:47 ` [PATCH bpf-next 8/8] selftests/bpf: switch tests to BTF-defined map definitions Andrii Nakryiko
2019-06-14 23:23   ` Stanislav Fomichev
2019-06-14 23:43     ` Andrii Nakryiko
2019-06-15  0:01       ` Stanislav Fomichev
2019-06-17 19:30         ` Andrii Nakryiko
2019-06-17 21:07           ` Stanislav Fomichev
2019-06-11  5:21 ` [PATCH bpf-next 0/8] BTF-defined BPF " Andrii Nakryiko

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